1. Field of the Invention
This invention relates to a substrate polishing method, and more particularly, to a substrate polishing method applied to flattening polishing of a polishing object in the form of a thin plate, such as a liquid crystal panel substrate.
The present invention also relates to a semiconductor device fabricated by applying the substrate polishing method and a fabrication method for the semiconductor device.
2. Description of the Related Art
In related art, a colloidal suspension, wherein silicon nitride or a hydrate of silicon nitride is dispersed colloidally or colloidal silica, is used as a polishing agent, that is, as a polishing composition (hereinafter referred to as slurry) for polishing the surface of a semiconductor substrate (hereinafter referred to as wafer) formed from a silicon wafer, a chemical wafer or the like. Further, as a polishing method, chemical mechanical polishing (CMP) is generally known wherein a wafer is placed on a polishing surface table on which a polishing cloth formed from a foamed member, a synthetic resin (polyurethane or the like) or an unwoven fabric is stretched and, while the wafer is pressed and rotated by a polishing head, the slurry is supplied quantitatively to the wafer to carry out polishing.
As the slurry, a solution produced by cracking silicon particles in the form of fine colloidal silica into a solution which contains an alkali component is used as disclosed, for example, in U.S. Pat. No. 3,328,141. This polishing applies a chemical action of an alkali component of a slurry, particularly an erosion action for a wafer or the like. In particular, by the erosion action of alkali, a thin and soft erosion layer is formed on the surface of a wafer or the like, and the thin layer is successively removed by the mechanical action of fine colloidal silicon particles to advance polishing.
Meanwhile, a polishing method for improving the flatness of an element isolation portion without an increase of the number of steps in trench element isolation formation by CMP is disclosed in Japanese Patent Laid-Open No. Hei 11-135617. According to the polishing method, a slurry formed from abrasive grains of a comparatively large particle size is used in the front half of polishing whereas another slurry formed from abrasive grains of a comparatively small particle size is used in the latter half to carry out polishing. Such polishing provides an effect that the polishing time is reduced by the polishing using abrasive grains of the comparatively large particle size and the flatness is improved by the polishing using abrasive grains of the comparatively small particle size.